The present invention relates to a partial injection apparatus, and more particularly, to such apparatus for obtaining a predetermined concentration of a test fluid to be obtained by adding a diluent to a sample or the like.
By way of example, in the field of a blood analysis, a blood corpuscle floating fluid to be used for either a reagent or a sample will be prepared by aspirating and ejecting either a blood corpuscle floating fluid of a desired concentration with a pipet or a blood corpuscle sample with a partial injector resorting to operations only for directly aspirating and ejecting a fluid of a desired amount.
However, in case of mixing the blood corpuscle sample and its diluent in a given volumetric ratio using either a pipet or a partial injector, the blood corpuscle sample being aspirated adheres to the inner wall thereof in a large amount, disadvantageously resulting in a decrease of the ejected amount compared with the amount aspirated and also resulting in a variation in the amount ejected. Thus, as a practical matter, a blood corpuscle floating fluid prepared with either the pipet or the partial injector will have a concentration which is lower than a desired value with the result that a precise analysis may not be performed. When a blood corpuscle floating fluid having the lower concentration has been prepared, the following measures should be taken to make it a desired concentration. Namely, by applying a centrifugation operation (for example, for five minutes at 3000 rpm) to the floating fluid, a designated amount of its supernatant fluid may be skimmed. Then the desired concentration must be obtained by agitating the remaining fluid again. These operations are troublesome and time consuming. On the other hand, it may be desirable to raise the concentration of the floating fluid by partially injecting an increment of the sample. It is impossible, however, to obtain precisely a desired concentration of the floating fluid since a partial injecting operation of an infinitesimal amount of the sample can not be effected precisely.